Using a self-assembly layer to facilitate selective formation of an etching stop layer

ABSTRACT

A structure is provided that includes a first conductive component and a first interlayer dielectric (ILD) that surrounds the first conductive component. A self-assembly layer is formed on the first conductive component but not on the first ILD. A first dielectric layer is formed over the first ILD but not over the first conductive component. A second ILD is formed over the first conductive component and over the first ILD. An opening is etched in the second ILD. The opening is at least partially aligned with the first conductive component. The first dielectric layer protects portions of the first ILD located therebelow from being etched. The opening is filled with a conductive material to form a second conductive component in the opening.

PRIORITY DATA

This application claims priority from U.S. Provisional PatentApplication No. 62/690,543, entitled “Using a Self-Assembly Layer toFacilitate Selective Formation of an Etching Stop Layer” and filed onJun. 27, 2018, the disclosure of which is incorporated herein in itsentirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. However, these advances haveincreased the complexity of processing and manufacturing ICs and, forthese advances to be realized, similar developments in IC processing andmanufacturing are needed. In the course of IC evolution, functionaldensity (i.e., the number of interconnected devices per chip area) hasgenerally increased while geometry size (i.e., the smallest componentthat can be created using a fabrication process) has decreased.

The decreased geometry sizes lead to challenges in semiconductorfabrication. For example, as geometry sizes continue to decrease,overlay control becomes more difficult, which could lead to reliabilityproblems and/or degraded device performance. As another example,conventional devices may have excessive parasitic capacitance.

Therefore, while existing semiconductor devices and the fabricationthereof have been generally adequate for their intended purposes, theyhave not been entirely satisfactory in every aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIGS. 1-2 are cross-sectional views of a semiconductor device at variousstages of fabrication according to embodiments of the presentdisclosure.

FIGS. 3A-3B are perspective views of a self-assembly layer and a surfaceon which it is formed according to various embodiments of the presentdisclosure.

FIGS. 4-9 are cross-sectional views of a semiconductor device at variousstages of fabrication according to embodiments of the presentdisclosure.

FIG. 10 is a perspective view of an example FinFET device.

FIG. 11 is a flow chart of a method for fabricating a semiconductordevice in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of thepresent disclosure. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the sake of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed. Moreover, various features may be arbitrarilydrawn in different scales for the sake of simplicity and clarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,elements described as being “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the exemplary term “below” can encompass both an orientation ofabove and below. The apparatus may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein may likewise be interpreted accordingly.

Still further, when a number or a range of numbers is described with“about,” “approximate,” and the like, the term is intended to encompassnumbers that are within a reasonable range including the numberdescribed, such as within +/−10% of the number described or other valuesas understood by person skilled in the art. For example, the term “about5 nm” encompasses the dimension range from 4.5 nm to 5.5 nm.

The present disclosure is generally directed to, but not otherwiselimited to, reducing or preventing problems associated with overlaycontrol. Overlay may refer to the alignment between various componentsof different layers in a semiconductor device such as an integratedcircuit (IC) chip. For example, an IC chip may include an interconnectstructure that is made up of a plurality of interconnect layers (alsoreferred to as different metallization layers). Each interconnect layermay include one or more conductive components—such as vias, contacts, ormetal lines—that are surrounded by an interlayer dielectric (ILD). Insome instances, a conductive component (e.g. a metal line or a via) ofone interconnect layer may need to be electrically connected to aconductive component (e.g., another via or another metal line) ofanother interconnect layer, and thus it is desirable for these twoconductive components to be aligned vertically. If overlay control isunsatisfactory, there may be a significant amount of misalignmentbetween the two conductive components, which could lead to problems suchas over-etching of the ILD, which in turn could cause reliability and/orperformance problems such as time-dependent dielectric breakdown (TDDB)or other leakage problems.

To overcome the problems discussed above, the present disclosureselectively forms a dielectric layer over an interconnect layer, suchthat the dielectric layer is formed on the upper surface of aninterlayer dielectric (ILD) but not on the upper surface of conductivecomponents (e.g., vias, contacts, or metal lines). This is achieved byfirst forming a self-assembly layer on the upper surfaces of theconductive components but not on the upper surface of the ILD. Theself-assembly layer prevents the formation of the dielectric layer onthe upper surfaces of the conductive components, for example by blockingthe precursors of a deposition process (e.g., atomic layer deposition)used to form the dielectric layer. The dielectric layer, which is formedon the ILD but not on the conductive component, serves as an etchingstop layer in a subsequent etching process that is performed to form avia hole that is supposed to be aligned with the conductive component.

As discussed above, in real world semiconductor fabrication, overlaycontrol may not be optimal, particularly as geometry sizes shrink, whichresults in a misalignment between the via hole and the conductivecomponent. Had the dielectric layer not been formed, the misalignmentcould have led to an undesirable etching of the ILD located below thevia hole and adjacent to the conductive component. However, according tothe various aspects of the present disclosure, the dielectric layerserves as an etching stop layer during the via hole etching process andprotects the portions of ILD located therebelow from being etched. Assuch, the resulting semiconductor device has better reliability and/orenhanced performance.

In some embodiments, the present disclosure may form a stack comprisingmultiple dielectric layers over the ILD. The dielectric layers in thestack may have different material compositions, for example differentdielectric constants. For example, a dielectric layer with a lowerdielectric constant is formed at the bottom of the stack while adielectric layer with a higher dielectric constant is formed at the topof the stack. The lower dielectric constant of the bottom layer may helpreduce a total capacitance associated with the stack.

The various aspects of the present disclosure will now be discussed inmore detail below with reference to FIGS. 1-11. In that regard, FIGS.1-2 and 4-9 are diagrammatic fragmentary cross-sectional side views of asemiconductor device at different stages of fabrication according toembodiments of the present disclosure, FIGS. 3A-3B are perspective viewsof a self-assembly layer, FIG. 10 is perspective view of an examplesemiconductor device on which the aspects of the present disclosure maybe implemented, and FIG. 11 is a flowchart illustrating a methodperformed according to embodiments of the present disclosure.

Referring now to FIG. 1, a portion of a semiconductor device 100 isillustrated. The semiconductor device 100 includes a substrate, whichmay be made of silicon or other semiconductor materials such asgermanium. The substrate also may comprise a compound semiconductor suchas silicon carbide, gallium arsenic, indium arsenide, or indiumphosphide. In some embodiments, the substrate may comprise alloysemiconductor such as silicon germanium, silicon germanium carbide,gallium arsenic phosphide, or gallium indium phosphide. In someembodiments, the substrate may include an epitaxial layer, for examplean epitaxial layer overlying a bulk semiconductor. Variousmicroelectronic components may be formed in or on the substrate, such astransistor components such as source/drain or gate, or isolationstructures such as shallow trench isolation (STI). Since the substrateand/or the microelectronic components formed therein or thereon are notthe focus of the present disclosure, the substrate is not specificallyillustrated herein for reasons of simplicity.

The semiconductor device 100 also include an interconnect layer 110. Theinterconnect layer 110 may be one of the interconnect layers in amulti-layered interconnect structure (MLI), which is formed over theaforementioned substrate and may include a plurality of patterneddielectric layers and conductive layers that provide interconnections(e.g., wiring) between the various microelectronic components of thesemiconductor device 100.

In the illustrated embodiment, the interconnect layer 110 includes aplurality of conductive components such as conductive components 120-122(note that the conductive components 121-122 are illustrated partiallyfor reasons of simplicity), as well as an interlayer dielectric (ILD)130 that surrounds the conductive components 120-122. The conductivecomponents 120-122 may include contacts, vias, or metal lines. In someembodiments, the conductive components 120-122 comprise conductivematerials such as aluminum, aluminum/silicon/copper alloy, titanium,titanium nitride, tungsten, polysilicon, metal silicide, or combinationsthereof. Alternatively, the conductive components 120-122 may includecopper, copper alloy, titanium, titanium nitride, tantalum, tantalumnitride, tungsten, polysilicon, metal silicide, or combinations thereof.

Meanwhile, the ILD 130 may include a low-k dielectric material (e.g., adielectric material having a dielectric constant that is smaller than adielectric constant of silicon dioxide, which is about 4). Asnon-limiting examples, the low-k dielectric material may include aporous organosilicate thin film such as SiOCH, tetraethylorthosilicate(TEOS) oxide, un-doped silicate glass, doped silicon oxide such asborophosphosilicate glass (BPSG), fused silica glass (FSG),phosphosilicate glass (PSG), fluorine-doped silicon dioxide,carbon-doped silicon dioxide, porous silicon dioxide, porouscarbon-doped silicon dioxide, silicon carbon nitride (SiCN), siliconoxycarbide (SiOC), spin-on organic polymeric dielectrics, spin-onsilicon based polymeric dielectrics, or combinations thereof. It isunderstood that a planarization process such as chemical mechanicalpolishing (CMP) may be performed to the interconnect layer 110 toflatten the upper surfaces of the conductive components 120-122 and theILD 130.

Referring now to FIG. 2, a self-assembly layer monolayer 200(hereinafter referred to as a self-assembly layer) is formed selectivelyover portions of the interconnect layer 110. For example, using aself-assembly layer formation process 210, the self-assembly layer 200is formed on the upper surfaces of the conductive components 120-122,but not on the upper surfaces of the ILD 130. In some embodiments, theself-assembly layer formation process 210 includes a chemical vapordeposition (CVD) process, a spin-on process, or a dipping process.

One reason for the selective formation of the self-assembly layer 200(e.g., on the conductive components 120 but not on the ILD 130) is thatthe self-assembly layer 200 includes a head group (also referred to asan anchor) that is configured to bond with the surfaces of a certainmaterial. For example, referring now to FIG. 3A, the self-assembly layer200 is illustrated in greater detail in a simplified 3-dimensionalperspective view. The self-assembly layer 200 is arranged into aplurality of strands, wherein each strand includes a head group 220 anda tail group 230 (also shown in FIG. 3B). The head group 220 has anaffinity with a certain material's surface, so that it bonds to thatsurface. In this case, the head group 220 is configured to have affinitywith a metal material but not with dielectric materials. As a result,the head group 220 bonds to the conductive component 120, which containsa metal material, but does not bond to the ILD, which contains adielectric material and not a metal material. In some embodiments, thehead group 220 may comprise phosphorous (P), sulfur (S), silicon (Si),or combinations thereof.

The tail group 230 is thermodynamically stable. Due to van-der Waalsforces among them, the tail group 230 are arranged into orderly andseparate strands of the self-assembly layer 200, where each strandextends in a vertically upward direction (though not necessarilyperpendicularly) facing away from the upper surface of the conductivecomponent 120. In some embodiments, the tail group 230 may comprise anorganic material, for example a carbon chain (e.g., a methyl group).

Referring now to FIG. 4, a dielectric layer formation process 250 isperformed to selectively form dielectric layers 300 and 301 over theupper surfaces of the semiconductor device 100. For example, thedielectric layers 300 and 301 are formed on the upper surfaces of theILD 130, but not on the upper surfaces of the conductive components120-122. The reason for the selective formation of the dielectric layers300 and 301 is that the self-assembly layer 200—which is formed on theupper surfaces of the conductive components 120-122—prevents theformation of the dielectric layer 300 and 301 thereon. For example, thedielectric layer formation process 250 may include a deposition processin which one or more precursors are used. The precursors may includechemicals that react with a surface of the material on which theprecursors are deposited. Through repeated exposures to the precursors,a thin film (such as the dielectric layers 300 and 301) may be slowlydeposited. According to the various aspects of the present disclosure,however, the unique structure of the self-assembly layer 200 on theupper surfaces of the conductive components 120-122 “blocks” theprecursors from being deposited thereon. As such, the precursors and inturn the entire dielectric layers 300 and 301—are formed over the ILD130 but not over the conductive components 120-122.

In some embodiments, the dielectric layer formation process 250 includesan atomic layer deposition (ALD) process. In other embodiments, thedielectric layer formation process 250 may include a chemical vapordeposition (CVD) process, a spin-on process, or an electro-less platingprocess. The dielectric layers 300 and 301 may include a dielectricmaterial that contains aluminum (Al), zirconium (Zr), yttrium (Y),hafnium (Hf), or combinations thereof. For example, the dielectriclayers 300 and 301 may include aluminum oxide, zirconium oxide, yttriumoxide, hafnium oxide, or combinations thereof. The dielectric layers 300and 301 have a relatively high dielectric constant, for example adielectric constant that is greater than the dielectric constant of theILD 130. In some embodiments where the dielectric layers 300 and 301contain an aluminum-based dielectric, the dielectric constant of thedielectric layers 300 and 301 is greater than about 9. In some otherembodiments where the dielectric layers 300 and 301 contain azirconium-based dielectric, yttrium-based dielectric, or a hafnium-baseddielectric, the dielectric constant of the dielectric layers 300 and 301is greater than about 25.

The high dielectric constant of the dielectric layers 300 and 301 helpsthe dielectric layers 300-301 achieve an etching selectivity with an ILD(to be formed later) that has also has a low-k dielectric material likethe ILD 130. For example, in an etching process to be performed later,the dielectric layers 300 and 301 and the low-k dielectric materialshould have substantially different etching rates. If the etching rateof the dielectric layers 300 and 301 is significantly smaller than theetching rate of the low-k dielectric material, the dielectric layers 300and 301 would serve as an effective etching stop layer. The aspect ofthe dielectric layers 300 and 301 functioning as etching stop layerswill be discussed in more detail below.

The dielectric layers 300 and 301 are also formed to each have athickness 310. In some embodiments, the thickness 310 is greater than 0nanometers (nm) but less than about 70 nm. In some embodiments, thethickness 310 is in a range between 0.1 nm and about 7 nm. Thisthickness range of the dielectric layers 300 and 301 is specificallytuned to allow the dielectric layers 300 and 301 to effectively serve asetching stop layers while not enlarging the size of the semiconductordevice 100 unnecessarily or interfering with the subsequent fabricationsteps.

In some embodiments, the self-assembly layer 200 is at least partiallyremoved after the formation of the dielectric layers 300 and 301. Forexample, the tail group 230 of the self-assembly layer 200 may beremoved using a thermal process (e.g., by heating the semiconductordevice 100), or by a plasma treatment, or by an application of achemical, such as a wet chemical that includes an aqueous solution or asolvent-based solution. In embodiments where the tail group 230 isremoved, the head group 220 still remains on the conductive components,forming a stable phase capping layer. In some embodiments, the tailgroup 230 need not be specifically removed by a targeted process, but itmay decompose during one or more subsequent processes.

Referring now to FIG. 5, a deposition process 350 is performed to forman etching stop layer 360 over the semiconductor device 100. In someembodiments, the deposition process 350 may include a CVD process, aphysical vapor deposition (PVD) process, an ALD process, or combinationsthereof. The etching stop layer 360 may be formed conformally over theremaining portions of the self-assembly layer 200 and over the sidesurfaces and upper surfaces of the dielectric layers 300 and 301. Insome embodiments, the etching stop layer 360 includes a dielectricmaterial, for example a dielectric material that is different from thematerial of the dielectric layers 300 and 301. In some embodiments, theetching stop layer 360 serves purposes such as adhesion, metal oxidationprevention, metal damage prevention, and universal etching performanceinsurance.

Referring now to FIG. 6, a deposition process 400 is performed to formanother ILD 430 over the etching stop layer 360. The deposition process400 may include a process such as CVD, PVD, ALD, or combinationsthereof. In some embodiments, the ILD 430 may include a low-k dielectricmaterial, such as SiOCH, TEOS, BPSG, FSG, etc. In some embodiments, theILD 130 and the ILD 430 have the same material composition.

Referring now to FIG. 7, an etching process 450 is performed to etch anopening 470 in the ILD 430, which extends vertically through the ILD430, the etching stop layer 360, and the self-assembly layer 200. Theetching process 450 may include a wet etching process or a dry etchingprocess. The opening 470 formed by the etching process 450 will befilled by a conductive material later, for example to form a conductivecomponent such as a via or a metal line. Ideally, the opening 470 shouldbe aligned with the conductive component 120, such that a goodelectrical connection can be established between the conductivecomponent 120 and the conductive component formed in the opening 470.

However, as is often the case in real world semiconductor fabrication,the alignment between the opening 470 and the conductive component 120is imperfect due to overlay control issues. This problem is furtherexacerbated as the geometry sizes shrink for each semiconductortechnology node. Consequently, as shown in FIG. 7, a misalignment existsbetween the opening 470 and the conductive component 120, which ismanifested as the opening 470 being shifted “to the right” such that theopening 470 is now located above a portion of the ILD 130. Inconventional semiconductor devices, such a misalignment may have led toan undesirable etching of the portion of the ILD 130 located under theopening 470 as a result of the etching process 450. The over-etchedportion of the ILD 130 would then be filled with the conductive materiallater when the conductive material fills the opening 470. This may causeproblems such as time-dependent dielectric breakdown (TDDB) or leakagewithin the semiconductor device 100.

The present disclosure overcomes the problem discussed above by formingself-aligned dielectric layers 300 and 301 on the ILD 130, which serveas etching stop layers herein to prevent the potential over-etching ofthe ILD 130 caused by the etching process 450. In more detail, as shownin FIG. 7, the etched opening 470 vertically extends through the ILD 430but stops at the dielectric layer 301. This is made possible by theetching selectivity between the dielectric materials of the dielectriclayer 301 and the ILD 430. As discussed above, the material compositionsof the dielectric layers 300-301 and the ILD 430 are configured suchthat a significant etching selectivity exists between them during theetching process 450. In some embodiments, the etching selectivitybetween the ILD 430 and the dielectric layer 301 is greater than about7:1. That is, the etching rate for the ILD 430 is at least 7 timesgreater than the etching rate for the dielectric layer 301 during theetching process 450. As such, the ILD 430 may be substantially etchedthrough without significantly affecting the dielectric layer 301, whichallows the dielectric layer 301 to serve as an etching stop layer (or aprotective layer) during the etching process 450. Since the dielectriclayer 301 is preserved, the portion of the ILD 130 located below thedielectric layer 301 is also protected from being etched.

Referring now to FIG. 8, a deposition process 500 is performed to form aconductive material 505 over the semiconductor device 100. Thedeposition process 500 may include a process such as CVD, PVD, ALD, orcombinations thereof. In some embodiments, the deposited conductivematerial 505 includes a metal or metal alloy such as copper, aluminum,tungsten, titanium, or combinations thereof. The deposited conductivematerial 505 and the ILD 430 may be considered portions of aninterconnect layer 510 of the multi-layer interconnect structure, whichis located above the interconnect layer 110. In some embodiments, theinterconnect layer 110 is a M_(n) (e.g., Metal-0) interconnect layer,and the interconnect layer 510 is a M_(n+1) (Metal-1) interconnectlayer.

A portion of the deposited conductive material 505 fills the opening 470to form a conductive element 520, while another portion of the depositedconductive material 505 serves as a metal line 530 for the interconnectlayer 510. In some embodiments, the conductive element 520 serves as aconductive via, which is electrically connected to the conductiveelement 120 below. Again, since the dielectric layer 301 serves as anetching stop layer during the etching of the via opening, the portion ofthe ILD 130 below the dielectric layer 301 is not etched. Therefore, thedeposition process 500 will not inadvertently form a conductive materialin the ILD 130, even if the conductive components 120 and 520 aremisaligned due to an overlay shift. In some embodiments, a planarizationprocess such as a CMP process may be performed to planarize an uppersurface of the metal line 530.

Note that at this stage of fabrication, a remnant of the self-assemblylayer 200 is still disposed on a portion of the conductive component 120that is not directly under the conductive component 520. In other words,a portion of the self-assembly layer 200 exposed by the via hole isetched away during the etching process 450, but the portions of theself-assembly layer 200 trapped between the conductive component 120-122and the etching-stop layer 360 are not affected by the etching process450 and therefore remain detectable in the final structure of thesemiconductor device 100. The presence of the self-assembly layer 200 isone of the unique physical characteristics of the present applicationand may indicate that the steps of the present disclosure discussedabove have been performed.

FIG. 9 illustrates an alternative embodiment of the present disclosurethat further improves the embodiment shown in FIG. 8. For reasons ofconsistency and clarity, similar components appearing in FIGS. 8 and 9are labeled the same. In the embodiment shown in FIG. 9, an extradielectric layer 550 is formed between the ILD 130 and the dielectriclayer 300, and an extra dielectric layer 551 is formed between the ILD130 and the dielectric layer 301. For example, after the selectiveformation of the self-assembly layer 200 (selectively formed on theconductive components 120-122 but not on the ILD 130), a depositionprocess is performed to form the dielectric layers 550-551 on the uppersurfaces of the ILD 130. The dielectric layers 550-551 are not formed onthe upper surfaces of the conductive components 120-122 due to thepresence of the self-assembly layer 200 on the upper surfaces of theconductive components 120-122. For example, the self-assembly layer 200may “block” the precursors of the dielectric layers 550-551 from beingdeposited thereon. As such, the precursors—and in turn the entiredielectric layers 550-551—are formed over the ILD 130 but not over theconductive components 120-122.

Similar to the dielectric layers 300 and 301, the dielectric layers 550and 551 may be formed by a process such as ALD, CVD, a spin-on process,or an electro-less plating process. The dielectric layers 550-551 mayinclude a dielectric material that contains Si, O, C, or as a dopedmixture with Al, Zr, Y, Hf, or combinations thereof. The dielectriclayers 550-551 are configured to achieve a relatively low dielectricconstant, for example a dielectric constant that is lower than thedielectric constant of the dielectric layers 300-301. In someembodiments, the dielectric constant of the dielectric layers 550 and551 is less than about 6, for example between about 4 and 6. In someother embodiments, the dielectric constant of the dielectric layers 550and 551 may be configured to be less than about 4.

One reason for forming the dielectric layers 550 and 551 is to lower thetotal parasitic capacitance of the semiconductor device 100. Asdiscussed above, the dielectric layers 300 and 301 have a relativelyhigh dielectric constant (e.g., greater than about 9 for Al-baseddielectric materials or greater than about 25 for Hf-based dielectricmaterials). Such a high dielectric constant may increase a parasiticcapacitance, which is positively correlated with dielectric constant. Ahigh parasitic capacitance may degrade the performance of thesemiconductor device 100, for example with respect to its speed and/orpower consumption.

The present disclosure alleviates the high parasitic capacitance problemthrough the implementation of the dielectric layers 550 and 551. Asdiscussed above, the dielectric layers 550 and 551 have a relatively lowdielectric constant. As such, the contribution to the total parasiticcapacitance from the dielectric layers 550 and 551 may be minimal.Furthermore, the presence of the dielectric layers 550 and 551effectively “elevates” the dielectric layers 300 and 301. Although thedielectric layers 300 and 301 have a relatively high dielectricconstant, their greater distance away from the ILD 130 (and from anelectric field associated with the breakdown voltage) lessens the impactor contribution to the total parasitic capacitance from the dielectriclayers 300 and 301. Consequently, the total parasitic capacitance islowered.

After the dielectric layers 550 and 551 are selectively formed on theupper surfaces of the ILD 130, the dielectric layers 300 and 301 areformed on the dielectric layers 550 and 551, respectively. Theself-assembly layer 200 still prevents the formation of the dielectricmaterials thereon (for example by blocking the precursors from beingdeposited thereon), and thus the dielectric layers 300-301 are formed onthe dielectric layers 550-551, respectively, but not on the conductivecomponents 120-122. The configuration of the dielectric layers 551 and301 in FIG. 9 simultaneously achieves both a low parasitic capacitance(due to the low dielectric constant of the dielectric layer 551) and ahigh etching selectivity with the ILD 430 (due to the high dielectricconstant of the dielectric layer 301).

As shown in FIG. 9, the dielectric layers 301 and 551 have a combinedthickness 570. In some embodiments, the thickness 570 is in a rangebetween about 0 nanometers and about 70 nanometers, for example between0.1 nm and about 15 nm. In some embodiments, the thickness of thedielectric layer 551 is also greater than a thickness of the dielectriclayer 301. These thicknesses are not arbitrary but are specificallyconfigured to achieve a sufficiently low total parasitic capacitancewithout affecting the etching stop functionality of the dielectric layer301.

The etching stop layer 360 is formed over the dielectric layers 300 and301, as well as over the conductive components 120-122. Thereafter, theILD 430 is formed, and the conductive component 520 is formed through anetching process to etch an opening in the ILD 430 and subsequentlyfilling the etched opening with a conductive material, in a mannersimilar to that described above in association with FIGS. 6-8. Similarto the embodiment discussed above with reference to FIG. 8, at least thedielectric layer 301 will serve as an etching stop layer during theetching of the opening, so as to protect the ILD 130 located below frombeing etched. The dielectric layer 551 may also help protect the ILD 130below during the etching process 450, but as discussed above, itsetching selectivity with ILD 430 is not quite as high, and thus theprimary function of the dielectric layer 551 is still to reduceparasitic capacitance, and serving as an etching stop layer is asecondary role for the dielectric layer 551.

The advanced lithography process, method, and materials described abovecan be used in many applications, including fin-type field effecttransistors (FinFETs). For example, the fins may be patterned to producea relatively close spacing between features, for which the abovedisclosure is well suited. In addition, spacers used in forming fins ofFinFETs, also referred to as mandrels, can be processed according to theabove disclosure.

For the sake of providing an example, a perspective view of an exampleFinFET device structure 800 is illustrated in FIG. 10. The FinFET devicestructure 800 includes two example FinFETs 815 and 825. In someembodiments, the FinFET 815 may be an N-type FinFET and the FinFET 825may be a P-type FinFET.

The FinFET device structure 800 includes a substrate 802. The substrate802 may be made of silicon, germanium or other semiconductor materials.The FinFET device structure 800 also includes one or more fin structures804 (e.g., Si fins) that extend from the substrate 802 in theZ-direction and surrounded by spacers 805 in the Y-direction. The finstructures 804 are each elongated in the X-direction and include asemiconductor material. The fin structure 804 may be formed by usingsuitable processes such as photolithography and etching processes. Insome embodiments, the fin structure 804 is etched from the substrate 802using dry etch or plasma processes. The fin structure 804 also includesan epi-grown material 811, which may (along with portions of the finstructure 804) serve as the source/drain regions of the FinFET devicestructure 800.

An isolation structure 808, such as a shallow trench isolation (STI)structure, is formed to surround the fin structure 804. A lower portionof the fin structure 804 is surrounded by the isolation structure 808,and an upper portion of the fin structure 804 protrudes from theisolation structure 808, as shown in FIG. 10. The isolation structure808 prevents electrical interference or crosstalk.

The FinFET device structure 800 further includes a gate stack structureincluding a gate electrode 810 and a gate dielectric layer (not shown)below the gate electrode 810. The gate electrode 810 may includepolysilicon or metal. Metal includes tantalum nitride (TaN), nickelsilicon (NiSi), cobalt silicon (CoSi), molybdenum (Mo), copper (Cu),tungsten (W), aluminum (Al), cobalt (Co), zirconium (Zr), platinum (Pt),or other applicable materials. In some embodiments, the gate electrode810 may be formed in a gate last process (or gate replacement process),in which a dummy polysilicon gate electrode is replaced by a metal gateelectrode. Hard mask layers 812 and 814 may be used to define the gateelectrode 810. A dielectric layer 816 may also be formed on thesidewalls of the gate electrode 810 and over the hard mask layers 812and 814. Portions of the dielectric layer 816 may serve as gate spacers.

The gate dielectric layer (not shown) may include dielectric materials,such as silicon oxide, silicon nitride, silicon oxynitride, dielectricmaterial(s) with high dielectric constant (high-k), or combinationsthereof. Examples of high-k dielectric materials include hafnium oxide,zirconium oxide, aluminum oxide, hafnium dioxide-alumina alloy, hafniumsilicon oxide, hafnium silicon oxynitride, hafnium tantalum oxide,hafnium titanium oxide, hafnium zirconium oxide, the like, orcombinations thereof.

It is understood that the gate stack structure may include additionallayers, such as interfacial layers, capping layers, diffusion/barrierlayers, or other applicable layers.

FIG. 11 is a flowchart of a method 900 for fabricating a semiconductordevice in accordance with various aspects of the present disclosure. Themethod 900 includes a step 910 of providing a structure that includes afirst conductive component and a first interlayer dielectric (ILD) thatsurrounds the conductive component.

The method 900 includes a step 920 of forming a self-assembly layer onthe first conductive component but not on the first ILD. In someembodiments, the self-assembly layer is formed by depositing theself-assembly layer that includes a head group and a tail group. In someembodiments, the head group comprises phosphorous, sulfur, or silicon.In some embodiments, the tail group comprises an organic material, whichmay include a carbon chain, such as a methyl group. In some embodiments,the tail group is removed in a later fabrication process, for example bya thermal process, by a plasma treatment, or by an application of achemical. In embodiments where the tail group is removed, the head groupstill remains on the conductive component as a capping layer.

The method 900 includes a step 930 of forming a first dielectric layerover the first ILD but not over the first conductive component. In someembodiments, the step 930 of forming the first dielectric layercomprises performing a deposition process using precursors. During theforming of the first dielectric layer, the self-assembly layer preventsthe precursors from being formed on the first conductive component.

The method 900 includes a step 940 of forming a second ILD over thefirst conductive component and over the first ILD.

The method 900 includes a step 950 of etching an opening in the secondILD, wherein the opening is at least partially aligned with the firstconductive component. The first dielectric layer protects portions ofthe first ILD located therebelow from being etched. In some embodiments,the etching step 950 is configured such that the second ILD has asubstantially greater etching rate than the first dielectric layer. Forexample, the second ILD may have an etching rate that is at least 7times greater than the etching rate of the first dielectric layer.

The method 900 includes a step 960 of filling the opening with aconductive material to form a second conductive component in theopening.

In some embodiments, before the forming of the first dielectric layer, asecond dielectric layer is formed on the first ILD. The self-assemblylayer prevents the second dielectric layer from being formed on thefirst conductive component, and the first dielectric layer is formed onthe second dielectric layer. In some embodiments, the second dielectriclayer is formed to have a lower dielectric constant than the firstdielectric layer. The total parasitic capacitance of the semiconductoris lowered by the lower dielectric constant of the second dielectriclayer, as well as the “elevation” of the first dielectric layer (whichhas a greater dielectric constant) since the first dielectric layer isformed on the second dielectric layer. In some embodiments, the seconddielectric layer is formed to have a greater thickness than the firstdielectric layer.

It is understood that additional process steps may be performed before,during, or after the steps 910-960 discussed above to complete thefabrication of the semiconductor device. For example, the method 900 mayinclude a step of forming an etching stop layer over the conductivecomponent and over the first ILD. The second ILD is formed over theetching stop layer.

For example, the method 900 may include the formation of source/drainregions and gate structures of a transistor before the step 910 isperformed, and the formation of additional interconnect layers,packaging, and testing, after the step 960 is performed. Other steps maybe performed but are not discussed herein in detail for reasons ofsimplicity.

In summary, the present disclosure forms a self-assembly layer onconductive elements (e.g., contacts, vias, or metal lines) of aninterconnect layer. The self-assembly layer has a head group that hasaffinity to the conductive material such as metal but not to dielectricmaterials, and thus the self-assembly layer is not formed on the ILDthat surrounds the conductive elements. Thereafter, a dielectric layeris formed, for example by a deposition process that uses precursors toform the dielectric layer. The self-assembly layer blocks the precursorsfrom being deposited thereon, thereby causing the dielectric material tobe formed on the ILD but not on the conductive elements. In this manner,the formation of the dielectric layer is “self-aligned” with the ILD.The material composition of the dielectric layer is configured such thata high etching selectivity exists between the dielectric layer and theILD in an etching process (e.g., the ILD is etched substantially fasterthan the dielectric layer) performed later. In some embodiments, a stackof at least two dielectric layers is formed on the ILD, where adielectric layer located at the bottom of the stack may have a lowerdielectric constant than the dielectric layer located at the top of thestack.

Based on the above discussions, it can be seen that the presentdisclosure offers advantages over conventional devices and thefabrication thereof. It is understood, however, that other embodimentsmay offer additional advantages, and not all advantages are necessarilydisclosed herein, and that no particular advantage is required for allembodiments.

One advantage is that the present disclosure alleviates problems causedby overlay shift. For example, a via hole may be etched in another ILDthat is formed above the dielectric layer, where the via hole ideallyshould be aligned with the conductive element. However, due to anoverlay shift, the via hole and the conductive element may bemisaligned. Had the selectively-formed dielectric layer not beenimplemented, such a misalignment would cause a portion of the ILDlocated below the via hole to be inadvertently etched. This could causereliability and/or performance problems such as breakdown voltage,time-dependent dielectric breakdown (TDDB), or leakage. Here, thedielectric layer serves as a self-aligned etching stop layer due to itslocation and high etching selectivity with the ILD. As a result, thedielectric layer protects portions of the ILD underneath from beingundesirably etched in the via hole etching process, which in turnimproves the reliability and/or performance of the semiconductor deviceherein.

Another advantage is associated with the embodiment where a stack ofdielectric layers is formed on the ILD. The bottom dielectric layer inthe stack has a low dielectric constant, which has a low contribution tothe total parasitic capacitance. The upper dielectric layer in the stackmay have a high dielectric constant, but its contribution to the totalparasitic capacitance is also minimized since it is “elevated” by thelower dielectric layer, which means it is farther away from the electricfield associated with the breakdown voltage. The reduction in totalparasitic capacitance also improves the performance of the semiconductordevice. Other advantages include compatibility with existing fabricationprocess flows, etc.

One aspect of the present disclosure involves a method of fabricating asemiconductor device. The method includes: providing a structure thatincludes a first conductive component and a first interlayer dielectric(ILD) that surrounds the first conductive component; selectively forminga self-assembly layer on the first conductive component; selectivelyforming a first dielectric layer over the first ILD; forming a secondILD over the first conductive component and over the first ILD; etchingan opening in the second ILD, wherein the opening is at least partiallyaligned with the first conductive component, wherein the firstdielectric layer protects portions of the first ILD located therebelowfrom being etched; and filling the opening with a conductive material toform a second conductive component in the opening.

One aspect of the present disclosure involves a semiconductor device.The semiconductor device includes: a first conductive component; a firstinterlayer dielectric (ILD) that surrounds the first conductivecomponent; a first dielectric layer disposed over the first ILD, whereinthe first dielectric layer has a greater dielectric constant than thefirst ILD; and a second conductive component disposed over, and at leastpartially aligned with, the first conductive component, wherein at leasta portion of the first dielectric layer is disposed between the firstILD and the second conductive component.

Another aspect of the present disclosure involves a semiconductordevice. The semiconductor device includes: a first metal element; afirst interlayer dielectric (ILD) that surrounds the first metalelement; a first dielectric layer disposed over the first ILD but notover the first metal element; a second dielectric layer disposed overthe first dielectric layer, wherein the second dielectric layer has agreater dielectric constant than the first dielectric layer; a secondILD disposed over the second dielectric layer, wherein an etchingselectivity exists between the second ILD and the second dielectriclayer; and a second metal element extending vertically through thesecond ILD, wherein the second metal element is at least partiallyaligned with, and electrically coupled to, the first metal element, andwherein a portion of the first dielectric layer or a portion of thesecond dielectric layer is disposed between the second metal element andthe first ILD.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device, comprising: a firstconductive component; a first interlayer dielectric (ILD) that surroundsthe first conductive component; a first dielectric layer disposed overthe first ILD, wherein the first dielectric layer has a greaterdielectric constant than the first ILD; a second conductive componentdisposed over, and at least partially aligned with, the first conductivecomponent, wherein at least a portion of the first dielectric layer isdisposed between the first ILD and the second conductive component; asecond ILD that surrounds the second conductive component, and whereinthe first dielectric layer has a lower etching rate than the second ILD;an etching stop layer that is disposed between the first dielectriclayer and the second ILD; and at least a portion of a self-assemblylayer disposed between the first conductive component and the etchingstop layer but not between the first conductive component and the secondconductive component.
 2. The semiconductor device of claim 1, furthercomprising: a second dielectric layer disposed between the firstdielectric layer and the first ILD.
 3. The semiconductor device of claim2, wherein the second dielectric layer has a lower dielectric constantthan the first dielectric layer.
 4. The semiconductor device of claim 1,wherein: the first conductive component includes a via or a metal lineof a first interconnect layer of a multilayer interconnect structure;and the second conductive component includes a via or a metal line of asecond interconnect layer of the multilayer interconnect structure, thesecond interconnect layer being located above the first interconnectlayer.
 5. The semiconductor device of claim 1, wherein the self-assemblylayer includes a head group that has an affinity with a metal materialbut not with dielectric materials.
 6. The semiconductor device of claim5, wherein the head group comprises phosphorous, sulfur, or silicon. 7.A semiconductor device, comprising: a first metal element; a firstinterlayer dielectric (ILD) that surrounds the first metal element; anentirety of a first dielectric layer disposed over the first ILD,wherein the entirety of the first dielectric layer is in direct contactwith the first ILD but is not disposed over the first metal element,wherein a first side surface of the first dielectric layer is inphysical contact with the first metal element, and wherein a second sidesurface of the first dielectric layer is in physical contact with anetching-stop layer; a second dielectric layer disposed over the entiretyof the entire first dielectric layer, wherein the entirety of the firstdielectric layer and the second dielectric layer have equal lateraldimensions; a second ILD disposed over the second dielectric layer,wherein an etching selectivity exists between the second ILD and thesecond dielectric layer; and a second metal element extending verticallythrough the second ILD, wherein the second metal element is at leastpartially aligned with, and electrically coupled to, the first metalelement, and wherein a portion of the second dielectric layer isdisposed directly below and in direct contact with the second metalelement.
 8. The semiconductor device of claim 7, wherein the secondmetal element is disposed on a first portion of an upper surface of thefirst metal element, and wherein the semiconductor device furthercomprises a self-assembly layer that is disposed over a second portionof the upper surface of the first metal element different from the firstportion.
 9. The semiconductor device of claim 8, further comprising anetching-stop layer disposed between the self-assembly layer and thesecond ILD.
 10. The semiconductor device of claim 8, wherein theself-assembly layer is arranged into a plurality of strands, and whereineach of the strands includes a head group and a tail group.
 11. Thesemiconductor device of claim 10, wherein the head group has an affinitywith a surface of a metal material but not with dielectric materials.12. The semiconductor device of claim 10, wherein the head groupcontains phosphorous, sulfur, or silicon, or combinations thereof. 13.The semiconductor device of claim 10, wherein the tail group includes anorganic material.
 14. The semiconductor device of claim 10, wherein eachof the strands extends in a direction facing away from an upper surfaceof the first metal element.
 15. The semiconductor device of claim 7,wherein the first dielectric layer has a dielectric constant that isless than about 6, and wherein the second dielectric layer has adielectric constant that is greater than about
 13. 16. The semiconductordevice of claim 7, wherein no metal elements are disposed directly belowthe first dielectric layer.
 17. A semiconductor device, comprising: afirst metal component; a first interlayer dielectric (ILD) thatsurrounds the first metal component, wherein the first ILD and the firstmetal component have co-planar upper surfaces; a first dielectric layerdisposed over the first ILD; and a second metal component disposed overa first portion of the first metal component; a self-assembly layerdisposed over a second portion of the first metal component, the secondportion being different from the first portion, wherein a bottom surfaceof the self-assembly layer is in direct contact with an upper surface ofthe second portion of the first metal component; an etching stop layerdisposed over the first ILD, over the first dielectric layer, and overthe self-assembly layer; and a second ILD disposed over the etching stoplayer, wherein the second ILD surrounds the second metal component. 18.The semiconductor device of claim 17, wherein: the self-assembly layeris arranged into a plurality of strands that extend away from an uppersurface of the first metal component; each of the strands includes ahead group and a tail group; and the head group has an affinity with thefirst metal component but not with the first ILD.
 19. The semiconductordevice of claim 18, wherein: the head group contains phosphorous,sulfur, or silicon, or combinations thereof; and the tail group includesan organic material.
 20. The semiconductor device of claim 17, whereinthe second metal component is mis-aligned with the first metalcomponent.